A form of pump and motor utilized in hydraulic power transmission comprises a rotor having a plurality of spaced radial vanes rotatable therewith and slidable relative thereto in slots provided in the rotor. The rotor and vanes cooperate with the internal contour of a cam to define one or more pumping chambers between the outer periphery of the rotor and the cam contour through which the vanes pass carrying fluid from an inlet port to an outlet port. Cheek plates are associated with each side of the cam and rotor through which the fluid flows to and from the rotor. The passages and grooves in the cheek plates along with the cam contour define the pump cycles or zones, namely, fill (inlet), precompression transition (inlet to pressure), displacement (discharge) and decompression (discharge to inlet).
It has heretofore been recognized that it is essential for efficient operation of the pump to apply a biasing pressure to a chamber at the underside of the vanes in order to maintain them in contact with the cam. In the past pressure has been applied continuously or intermittently to the undersides of the vanes. In the continuous pressure arrangement pressure is applied even when the vanes are in low pressure zones and has resulted in excessive cam and vane tip wear. In the intermittent pressure arrangement, pressure is applied to the vanes only when the vanes are in high pressure zones and only centrifugal force is utilized to urge the vanes toward the cam when the vanes are in low pressure zones; such a vane system is described in U.S. Pat. No. 3,869,231, which possesses one undervane surface that is subjected to intermittent pressure. As a result, the contact of the vanes with the cam is not positive during some portion of the travel so that efficiency and wear are adversely affected.
It has heretofore been suggested and commercial devices have been made wherein additional pressure chambers are associated with each vane. The chamber at the base of each vane is commonly known as the undervane chamber and is subjected to cyclically changing pressure. The additional chambers are commonly known as the intra-vane chambers and are subjected to continuous high pressure. Typical devices are shown in U.S. Pat. Nos. 2,919,651, 2,967,488, 3,102,494, 3,103,893, 3,421,413, 3,447,477, 3,645,654, 3,752,609, 4,431,389 and 4,505,654. In such an arrangement the contact of the vanes with the cam is controlled at all times by fluid pressure to the intra-vane and corresponding undervane chambers.
It has generally been thought that such systems operate most sufficiently at pressure applications of about 3,000 psi. However, in certain environments it is desirable to obtain higher pressures.
Accordingly, among the objectives of the present invention are to provide a pressure energy translating device in the form of a vane type pump or motor which will operate at higher pressures; which will have increased rotor segmental strength; which will have lesser tendency for vane pinch by the loaded rotor segments; which will be less sensitive to radial unbalance as a result of vane tip wear; which will provide strategic undervane porting to achieve more positive vane tracking of the cam contour; and which will provide a smaller diameter rotor thereby maximizing the rated speed (rpm).
In accordance with the invention a fluid pressure energy translating device of the sliding vane type comprises a cam ring including an internal contour, a rotor having a plurality of vanes rotatable therewith and slidable relative thereto in slots in the rotor with one end of each vane engaging the internal contour. The rotor and internal contour cooperate to define one or more pumping chambers between the periphery of the rotor and the cam contour through which the vanes pass carrying fluid from an inlet port to an outlet port. Two or more pressure undervane chambers are formed for each vane. One of these chambers is of a controlled area and is to continuous discharge pressure to urge the vanes into engagement with the cam. The leading (direction of rotation) pressure sensing passages extend from the periphery of the rotor and communicate the respective pressure of the intervane volume to the remaining undervane chamber during all the events of the pumping cycle. The end to each vane is tapered with the radially outermost portion of the end extending in a trailing manner. The leading passages also provide paths for exhausting the undervane displacement to ensure hydrostatic bias on the vane; this biased pressure is distributed to cause the vanes in the discharge zone to maintain contact on the cam contour.